Present orifice chambers utilize an assembly of a number of orifice chambers having orifice plates to progressively reduce the operating pressure of large gas flows, typically flue gas operating from 20 to 40 psig at temperatures ranging from 500 to 1500.degree. F., to atmospheric pressure. Each orifice chamber is equipped with one or more orifices or perforated plates, and typically the assembly has a minimum of two and a maximum of seven orifice chambers having orifice plates in order to progressively take small pressure drops across the orifice plates in each of the orifice chambers in lieu of one large pressure drop. The size of the orifice chambers ranges typically from 30 inches in diameter to 130 inches in diameter. The flowing medium is typically flue gas from a catalytic cracking unit going to the stack outlet of a refinery. The flue gas is a result of the combustion process in a regenerator of a catalytic cracking unit.
The orifice or perforated plates of the orifice chambers require periodic inspection and maintenance and therefore are equipped with a manway or manhole for access to each orifice chamber and the orifice plates or plates secured therein for inspection and maintenance such as repair or replacement, which requires opening and closing each manway or manhole, is time consuming and expensive.
In the following prior art, U.S. Pat. No. 3,712,502 discloses a tanker having internal compartments formed by internal sections 2 which may be welded therein and having openings 10 therethrough; U.S. Pat. No. 3,050,315 discloses a tank having spaced perforated surge plates 4 mounted therein; U.S. Pat. No. 4,611,724 discloses a fluid storage tank with internal welded baffles 20 and perforations to permit fluid to flow through the baffles; U.S. Pat. No. 5,346,092 discloses a tank having welded interior separators 13, 14 and one manhole 12 secured to an inner tank section; U.S. Pat. No. 2,092,490 discloses a welding of interior separating plate 22 within a tank.
The following U.S. Pat. Nos. 710,405, 1,613,746, 1,952,867, 3,250,319, 3,338,238, and 3,425,810 disclose various arrangements for mounting welded interior sections or providing perforations within the sections all within larger chambers.
None of the foregoing prior art orifice chambers and patents disclose or suggest an assembly of orifice chambers for a gradual, progressive, and sequential reduction of operating gas pressures as it flows through a plurality of orifice chambers having removable orifice plates in the orifice chambers and a single access manway or manhole to a first orifice chamber, and access to successive chambers is provided by sequential removal of the orifice plates for maintenance, such as for inspection, repair, and replacement.
It would be highly desirable to provide an improvement in the present assemblies of such orifice chambers which would require only one manway or manhole for the entire assembly for maintenance such as inspection, repair, and replacement of the orifice or perforated plates.